Dialysis Machines

Dialysis machines

 

Machines used to perform hemodialysis are of different varieties. The following fuctions are carried out by these machine

Proportionate mixing of dialysate concentrate and treated water to form dialysate. The composition of dialysate is similar to blood without cells, proteins, lipids and some other complex salts. The dialysate consists mainly of water and various main salts and ions eg sodium, potassium, chloride , bicarbonate, calcium etc.

The dialysate is freed of dissolved gases, and is heated to body temperature. Very low temperature may cause hypothremia and high temperature of dialysated may cause fever.

These machines has a self cleaning mechanism with hot water and various chemicals to take care of various pathogens.

It pulls blood at speeds set by the dialysis personnel and also supplies dialysate at required rate. It can also create negative pressure so that extra fluid can be removed from the body.

During dialysis a person may require various medicines to be administered. This is facilitated by the machine.

Additionally, machines have safety measures. It can detect air in blood so that air does not enter patients’ blood vessels. The machines go into auto shut mode if air is detected in returning blood.

If blood gets hemolysed (hemoglobin leaks out of RBCs) a serious situation for a patient may develop. Machines can detect leaked hemoglobin and sound an alarm.

Most newer machines have built in blood pressure monitoring system. If blood pressure becomes lower or higher than set range, an alarm is sounded and corrective measures can be taken.

Machines also monitor the flow of blood from the patient. If the pressure in the tubing is recorded higher or lower than set limits, alarms sound for the call to dialysis nurse or technician.

Modern machines can also measure dialysis dose. (more about this later in dialysis adequacy)

Next topic in dialysis series is dialysers.

Dialysis Water

Dialysis water

During hemo-dialysis about 500 ml (range 50-800 ml) of dialysate flows through the dialyer (The plastic casing that contains dialysis membrane and which partitions blood on one side and dialysate on the other).

Water treatment is an essential requisite for safe dialysis.

In a 4 to 5 hrs session about 120 to 150 liters of water thus comes into contact with blood.

A very small impurity in this water thus can get magnified and produce serious consequences in the renal failure patient.

If dialysis water is unfit, it results in recurrent fever, poor health and nutrition of patient, electrolyte abnormalities etc. High aluminium levels can produce brain disorder called dementia and aluminium related bone disease. High chlorine levels can cause severe reactions.

Water treatment is done for ensuring safe dialysis water.

If ground or municipal supply provides hard water it is softened by machine.

Particulate matter is removed by filters consisting of pebbles, sand and other materials first so that large particles are removed, small particles than are removed by microfilters which can remove 5-micron size particles.

Chlorine is removed by adsorption on to carbon particles. It should be present in water before it is treated but removed during water treatment.

Excessive salts are measured as TDS (total dissolved solids) expressed as parts per million or ppm in short.Both cations and anions measured and TDS is equal to about 100 X total ions expressed as milliequivalents. It is usually 0.5 to 1 times the conductivity value.

Bacteria and their products produce harmful substances. These need to be removed and water prevented from letting them grow again by regular maintenance of the pipes and drainage system.

To produce water of sufficiently good quality, various criteria have been laid by different countries. AAMI dialysis criteria is one such criteria. In these acceptable levels of various chemicals and other impurities are mentioned.

Good quality dialysis water reduces morbidity, mortality, and complications in dialysis. It results in better overall health and quality of life for the patient.